In the art of fabricating integrated circuits, it is well known that continuing goals are to make the circuit and the associated package smaller, more dense, more thermally efficient, and lower cost. A number of alternate packaging methodologies have been proposed to address these and other areas of concern. The module or casing in which the integrated circuit or IC is packaged is an important factor in the ultimate cost, performance, and lifetime of the integrated circuit. For example, as ICs become more dense, efficient dissipation of thermal energy generated by the chip becomes increasingly important in extending their useful life as far as possible. Another consideration is the increasing number of leads and connections to the integrated circuit pads, which correspondingly increases the complexity of the construction and adds to the cost of the end product. Increased density is also manifested by increases in size of the physical package. Because the size of the package is an exponential function of the number of leads emanating from the die, increasing density rapidly and dramatically increases the package size. Larger die and package sizes create increased thermal problems due to mismatch of the expansion coefficients of the packaging materials.
Transfer molding IC die in plastic packages such as dual in-line packages (DIP) or quad flat packs (QFP) creates significant problems when the DIP or QFP becomes large. Problems, such as heat management and expansion coefficient stresses, limit the upper size of the package. Numerous schemes have been proposed to address these problems, for example, adding appropriate fillers to the plastic molding compound to enhance thermal transfer. Fillers also reduce the expansion coefficient to more closely approximate that of the silicon IC. These methods have not been widely adopted by the industry since they do not totally address and appropriately solve all the problems.
Thus, a continuing goal in the art of providing packages for electronic components such as integrated circuits is a package design that addresses thermal management and thermal expansion coefficient mismatch problems satisfactorily in an arrangement that can be reliably manufactured at a low cost. Such a package has not previously been in existence for large integrated circuit packages.